In order to provide adequate electrical contact between common household electrical plugs and the corresponding electrical receptacles, it has been common to provide a sliding contact between the pins of the electrical plug and a substantial length of the mating contacts in the receptacle. This sliding contact takes place at an extended length of a central portion of the receptacle contacts and the pins of the plug. In order to assure an adequate, low-resistance contact, the receptacle contacts are generally bifurcated so as to grasp and hold the pin between two contact elements arranged to exert a closing force on the pin. While such prior art receptacles have normally provided adequate electrical contact with the pins of the mating plug, such contact deteriorates under environmental conditions where the wiping surface of the bifurcated contacts may become coated with nonconductive material. More importantly, such prior art electrical receptacles initiate electrical contact while the pins are inserted into the receptacle only a small portion of their entire length. It is therefore possible to inadvertently touch an exposed portion of the plug pins and receive an electrical shock. This is a particular danger for small children or elderly persons who have difficulty in removing the plug and tend to insert their fingers under the plug to assist in removal. Small children also tend to play with electrical plugs, thereby increasing the danger.
It would be an improvement from a safety viewpoint to permit electrical contact inside of an electrical receptacle only after the pins have been inserted substantially all of the way into the receptacle, leaving very little of the pin length exposed. Unfortunately, the tips of the pins tend to vary in size and position to such an extent that a solid electrical contact cannot be guaranteed if only the tips of the pins are used to make contact. Worse, such tip-only contacts tend to be intermittent, damaging the electrical appliances connected to the plug.